Initial Commit

openssl-1.0.2f/doc/crypto/threads.pod

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+=pod
+
+=head1 NAME
+
+CRYPTO_THREADID_set_callback, CRYPTO_THREADID_get_callback,
+CRYPTO_THREADID_current, CRYPTO_THREADID_cmp, CRYPTO_THREADID_cpy,
+CRYPTO_THREADID_hash, CRYPTO_set_locking_callback, CRYPTO_num_locks,
+CRYPTO_set_dynlock_create_callback, CRYPTO_set_dynlock_lock_callback,
+CRYPTO_set_dynlock_destroy_callback, CRYPTO_get_new_dynlockid,
+CRYPTO_destroy_dynlockid, CRYPTO_lock - OpenSSL thread support
+
+=head1 SYNOPSIS
+
+ #include <openssl/crypto.h>
+
+ /* Don't use this structure directly. */
+ typedef struct crypto_threadid_st
+         {
+         void *ptr;
+         unsigned long val;
+         } CRYPTO_THREADID;
+ /* Only use CRYPTO_THREADID_set_[numeric|pointer]() within callbacks */
+ void CRYPTO_THREADID_set_numeric(CRYPTO_THREADID *id, unsigned long val);
+ void CRYPTO_THREADID_set_pointer(CRYPTO_THREADID *id, void *ptr);
+ int CRYPTO_THREADID_set_callback(void (*threadid_func)(CRYPTO_THREADID *));
+ void (*CRYPTO_THREADID_get_callback(void))(CRYPTO_THREADID *);
+ void CRYPTO_THREADID_current(CRYPTO_THREADID *id);
+ int CRYPTO_THREADID_cmp(const CRYPTO_THREADID *a,
+                         const CRYPTO_THREADID *b);
+ void CRYPTO_THREADID_cpy(CRYPTO_THREADID *dest,
+                          const CRYPTO_THREADID *src);
+ unsigned long CRYPTO_THREADID_hash(const CRYPTO_THREADID *id);
+
+ int CRYPTO_num_locks(void);
+
+ /* struct CRYPTO_dynlock_value needs to be defined by the user */
+ struct CRYPTO_dynlock_value;
+
+ void CRYPTO_set_dynlock_create_callback(struct CRYPTO_dynlock_value *
+	(*dyn_create_function)(char *file, int line));
+ void CRYPTO_set_dynlock_lock_callback(void (*dyn_lock_function)
+	(int mode, struct CRYPTO_dynlock_value *l,
+	const char *file, int line));
+ void CRYPTO_set_dynlock_destroy_callback(void (*dyn_destroy_function)
+	(struct CRYPTO_dynlock_value *l, const char *file, int line));
+
+ int CRYPTO_get_new_dynlockid(void);
+
+ void CRYPTO_destroy_dynlockid(int i);
+
+ void CRYPTO_lock(int mode, int n, const char *file, int line);
+
+ #define CRYPTO_w_lock(type)	\
+	CRYPTO_lock(CRYPTO_LOCK|CRYPTO_WRITE,type,__FILE__,__LINE__)
+ #define CRYPTO_w_unlock(type)	\
+	CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_WRITE,type,__FILE__,__LINE__)
+ #define CRYPTO_r_lock(type)	\
+	CRYPTO_lock(CRYPTO_LOCK|CRYPTO_READ,type,__FILE__,__LINE__)
+ #define CRYPTO_r_unlock(type)	\
+	CRYPTO_lock(CRYPTO_UNLOCK|CRYPTO_READ,type,__FILE__,__LINE__)
+ #define CRYPTO_add(addr,amount,type)	\
+	CRYPTO_add_lock(addr,amount,type,__FILE__,__LINE__)
+
+=head1 DESCRIPTION
+
+OpenSSL can safely be used in multi-threaded applications provided
+that at least two callback functions are set, locking_function and
+threadid_func.
+
+locking_function(int mode, int n, const char *file, int line) is
+needed to perform locking on shared data structures. 
+(Note that OpenSSL uses a number of global data structures that
+will be implicitly shared whenever multiple threads use OpenSSL.)
+Multi-threaded applications will crash at random if it is not set.
+
+locking_function() must be able to handle up to CRYPTO_num_locks()
+different mutex locks. It sets the B<n>-th lock if B<mode> &
+B<CRYPTO_LOCK>, and releases it otherwise.
+
+B<file> and B<line> are the file number of the function setting the
+lock. They can be useful for debugging.
+
+threadid_func(CRYPTO_THREADID *id) is needed to record the currently-executing
+thread's identifier into B<id>. The implementation of this callback should not
+fill in B<id> directly, but should use CRYPTO_THREADID_set_numeric() if thread
+IDs are numeric, or CRYPTO_THREADID_set_pointer() if they are pointer-based.
+If the application does not register such a callback using
+CRYPTO_THREADID_set_callback(), then a default implementation is used - on
+Windows and BeOS this uses the system's default thread identifying APIs, and on
+all other platforms it uses the address of B<errno>. The latter is satisfactory
+for thread-safety if and only if the platform has a thread-local error number
+facility.
+
+Once threadid_func() is registered, or if the built-in default implementation is
+to be used;
+
+=over 4
+
+=item *
+CRYPTO_THREADID_current() records the currently-executing thread ID into the
+given B<id> object.
+
+=item *
+CRYPTO_THREADID_cmp() compares two thread IDs (returning zero for equality, ie.
+the same semantics as memcmp()).
+
+=item *
+CRYPTO_THREADID_cpy() duplicates a thread ID value,
+
+=item *
+CRYPTO_THREADID_hash() returns a numeric value usable as a hash-table key. This
+is usually the exact numeric or pointer-based thread ID used internally, however
+this also handles the unusual case where pointers are larger than 'long'
+variables and the platform's thread IDs are pointer-based - in this case, mixing
+is done to attempt to produce a unique numeric value even though it is not as
+wide as the platform's true thread IDs.
+
+=back
+
+Additionally, OpenSSL supports dynamic locks, and sometimes, some parts
+of OpenSSL need it for better performance.  To enable this, the following
+is required:
+
+=over 4
+
+=item *
+Three additional callback function, dyn_create_function, dyn_lock_function
+and dyn_destroy_function.
+
+=item *
+A structure defined with the data that each lock needs to handle.
+
+=back
+
+struct CRYPTO_dynlock_value has to be defined to contain whatever structure
+is needed to handle locks.
+
+dyn_create_function(const char *file, int line) is needed to create a
+lock.  Multi-threaded applications might crash at random if it is not set.
+
+dyn_lock_function(int mode, CRYPTO_dynlock *l, const char *file, int line)
+is needed to perform locking off dynamic lock numbered n. Multi-threaded
+applications might crash at random if it is not set.
+
+dyn_destroy_function(CRYPTO_dynlock *l, const char *file, int line) is
+needed to destroy the lock l. Multi-threaded applications might crash at
+random if it is not set.
+
+CRYPTO_get_new_dynlockid() is used to create locks.  It will call
+dyn_create_function for the actual creation.
+
+CRYPTO_destroy_dynlockid() is used to destroy locks.  It will call
+dyn_destroy_function for the actual destruction.
+
+CRYPTO_lock() is used to lock and unlock the locks.  mode is a bitfield
+describing what should be done with the lock.  n is the number of the
+lock as returned from CRYPTO_get_new_dynlockid().  mode can be combined
+from the following values.  These values are pairwise exclusive, with
+undefined behaviour if misused (for example, CRYPTO_READ and CRYPTO_WRITE
+should not be used together):
+
+	CRYPTO_LOCK	0x01
+	CRYPTO_UNLOCK	0x02
+	CRYPTO_READ	0x04
+	CRYPTO_WRITE	0x08
+
+=head1 RETURN VALUES
+
+CRYPTO_num_locks() returns the required number of locks.
+
+CRYPTO_get_new_dynlockid() returns the index to the newly created lock.
+
+The other functions return no values.
+
+=head1 NOTES
+
+You can find out if OpenSSL was configured with thread support:
+
+ #define OPENSSL_THREAD_DEFINES
+ #include <openssl/opensslconf.h>
+ #if defined(OPENSSL_THREADS)
+   // thread support enabled
+ #else
+   // no thread support
+ #endif
+
+Also, dynamic locks are currently not used internally by OpenSSL, but
+may do so in the future.
+
+=head1 EXAMPLES
+
+B<crypto/threads/mttest.c> shows examples of the callback functions on
+Solaris, Irix and Win32.
+
+=head1 HISTORY
+
+CRYPTO_set_locking_callback() is
+available in all versions of SSLeay and OpenSSL.
+CRYPTO_num_locks() was added in OpenSSL 0.9.4.
+All functions dealing with dynamic locks were added in OpenSSL 0.9.5b-dev.
+B<CRYPTO_THREADID> and associated functions were introduced in OpenSSL 1.0.0
+to replace (actually, deprecate) the previous CRYPTO_set_id_callback(),
+CRYPTO_get_id_callback(), and CRYPTO_thread_id() functions which assumed
+thread IDs to always be represented by 'unsigned long'.
+
+=head1 SEE ALSO
+
+L<crypto(3)|crypto(3)>
+
+=cut